(a) Field of the Invention
The present invention relates to a system and a method of controlling the operation of a motor vehicle. More particularly, the present invention relates to a system and a method of controlling the operation of a hybrid motor vehicle that changes a filter coefficient for determining a demand torque desired by a driver according to the current driving condition of the vehicle.
(b) Description of the Related Art
In developing logic for controlling the operation of a hybrid vehicle, logic that calculates a demand torque for a driver should reflect the driver's intention precisely. The intention of the driver with respect to hybrid vehicle operation parameters such as, for example, acceleration, deceleration, maintaining a speed, etc., should be carried out by the logic so as to drive the vehicle in the manner the driver requests. If the logic calculates a demand torque that does not fully reflect the intention of the driver, then the vehicle will be driven in a manner different from the intention of the driver. Consequently, drivability of the vehicle may be decreased, while the risk of an accident increases. In view of the foregoing, it is clear that it is important to ensure that the logic calculates the demand torque for the driver's request precisely.
Generally, the driver's request may be understood based on data values detected by an acceleration pedal position sensor (APS) and a brake pedal position sensor (BPS). An acceleration torque may be calculated by multiplying a sum of a minimum torque and a maximum torque, and the value detected by the APS. As shown in FIG. 1, if the minimum torque is −60 Nm, the maximum torque is 200 Nm, and the value detected by the APS is 50%, the acceleration torque is 70 Nm ((−60+200)*0.5). In addition, a deceleration torque may be calculated based on the value detected by the BPS. That is, the regenerative braking amount and hydraulic braking amount may be determined based on the value detected by the BPS, and the deceleration torque is calculated according to the regenerative braking amount and the hydraulic braking amount from a predetermined function.
If the driver wants to accelerate, the acceleration torque may be increased proportionally to the value detected by the APS. On the other hand, if the driver wants to decelerate, the value detected by the BPS increases. The demand torque that corresponds to the driver's request, and is suitable for the current operation of the vehicle, may be calculated by considering the current gear and vehicle speed, in addition to the values detected by the APS and the BPS. When calculating the demand torque for the driver's request, the demand torque should be filtered so as not to be changed too rapidly, and the filtered demand torque should be controlled so as not to deviate from the driver's request. In addition, the demand torque should not be calculated by filtering the demand torque excessively or else it may differ from the driver's request.
According to the conventional method for calculating a demand torque, the creep torque may be set as the minimum torque that allows vehicle creeping when the value detected by the APS is 0%, and the sum of the maximum engine torque and the maximum motor torque may be set as the maximum torque. In other words, the minimum torque is the torque when the APS value is 0%, and the maximum torque is the torque when the APS value is 100%. The demand acceleration torque is calculated according to the vehicle speed and the APS value, and the calculated demand acceleration torque is filtered by a constant filter coefficient so as not to be changed too rapidly. Unfortunately, the conventional art filters the demand torque with a constant filter coefficient as shown in FIG. 1, which means that the current driving condition is not fully reflected by the resulting filtered demand torque. For example, when a signal is input from a traction control system (TCS) or an electronic stability program (ESP), the demand torque should directly reflect the intention of the driver quickly for safety. However, since the conventional art implements a filter coefficient with a fixed value, the current driving condition is not accurately reflected quickly in the demand torque response, and the driver may not be able to operate the vehicle safely.